The functional role of lymphoid cells, including the macrophages (M phi) and T and B lymphocytes and their soluble mediators in the induction of an IgA immune response will be studied in vitro. Optimal in vitro culture conditions for enumeration of IgA antibody (plaque) forming cells (PFC) following stimulation with T dependent antigens including DNP-Streptococcus mutans and TNP-erythrocytes, and lipopolysaccharide (LPS) as adjuvant from tissues including Peyer's patches (PP), mesenteric lymph nodes (MN), cervical lymph nodes (CN) and spleen (S) from CH3/HeN and C3H/HeJ mice will be evaluated. Single cell preparations or purified T and B cells from PP, MN, CN or S and M phi from spleen or peritoneum of E. coli K235 monoassociated mice will be immunized and incubated in Mishell-Dutton type cultures with LPS as adjuvant. The importance of monocyte (LAF monokine) and T cell (TRF) mediators and LPS on the induction of kinins, and their involvement in an IgA response will be established. The origin of precursor IgA B cells and T cells in mucosal tissues including the saliva glands will be determined by examination of homing patterns of lymphocytes from gut-associate lymphoid-tissue (GALT) and MN, CN and other sources. Cell tranfer experiments utilizing radioisotope methodology will be performed in groups of rats that are gnotobiotic, B cell suppressed, irradiated, or conventionalized in order to determine the origin of precursor lymphocytes. Furthermore, the efficacy of various modes of immunization in inducing antibodies in secretions will be assessed by tracing the homing patterns of antigen-sensitized cells to their sites of expression and by quantitating the immunological response utilizing fluorescent microscopy and serological techniques.